查看委託沒有被調用

Question

我建立一個圖形應用程序，我有一個觀點和一個視圖控制器，它充當視圖的委託（檢索信息）。雖然我還沒有開始實際的繪圖，但我正在嘗試將值存儲在字典中;然而，我有一些NSLogs有條不紊地放置在視圖控制器中，我注意到我從視圖中調用的委託方法根本沒有被調用。例如，我打電話給我的scaleForGraph函數，但它不執行。作爲新手，我不確定是否有某些我錯過了。僅供參考：我沒有錯誤，它編譯並執行。我試圖儘可能減少代碼。感謝您的幫助！

下面是我的看法，我在那裏定義協議的.H：

// GraphView.h 

#import <UIKit/UIKit.h> 

@class GraphView; 

@protocol GraphViewDelegate <NSObject> 
- (float)scaleForGraph:(GraphView *)requestor; 
-(NSMutableDictionary*) valuesForGraph:(GraphView *)requestor withWidth:(float) width; 

@end 

@interface GraphView : UIView 
@property (nonatomic) id <GraphViewDelegate> delegate; 
@property (nonatomic) id expressionCopy; 

@end 

而這裏的.M：

#import "GraphView.h" 

@implementation GraphView 
@synthesize expressionCopy = _expressionCopy; 

- (id)initWithFrame:(CGRect)frame 
{ 
    self = [super initWithFrame:frame]; 
    if (self) { 
     // Initialization code 
     self.contentMode = UIViewContentModeRedraw; 
    } 
    return self; 
} 

- (void)awakeFromNib 
{ 
    self.contentMode = UIViewContentModeRedraw; 
} 

// Only override drawRect: if you perform custom drawing. 
// An empty implementation adversely affects performance during animation. 
- (void)drawRect:(CGRect)rect 
{ 
    CGContextRef c = UIGraphicsGetCurrentContext(); 
    CGRect screenBound = [[UIScreen mainScreen] bounds]; 
    CGSize screenSize = screenBound.size; 
    CGFloat width = screenSize.width; 
    CGFloat height = screenSize.height; 
    float scale = [self.delegate scaleForGraph:self]; 
    NSLog([NSString stringWithFormat:@"My Scale: %f",scale]); //always returns 0 
    NSMutableDictionary *graphValues = [self.delegate valuesForGraph:self withWidth:width]; 
} 
@end 

這是我的視圖控制器的.h：

#import <UIKit/UIKit.h> 
#import "GraphView.h" 

@interface GraphingViewController : UIViewController <GraphViewDelegate> 
@property (weak, nonatomic) IBOutlet GraphView *graphView; 
@property (strong, nonatomic) IBOutlet UIStepper *stepper; 
- (IBAction) changedScale:(UIStepper *)stepper; 
@property (nonatomic) int scale; 
@property (nonatomic) id expressionCopy; 
@end 

下面是對控制器的.m：

#import "GraphingViewController.h" 
@interface GraphingViewController() 

@end 

@implementation GraphingViewController 
@synthesize expressionCopy = _expressionCopy; 

- (void)updateUI 
{ 
    self.stepper.value = self.scale; 
    [self.graphView setNeedsDisplay]; 
} 

- (void)setScale:(int)scale 
{ 
    if (scale < 0) scale = 0; 
    if (scale > 100) scale = 100; 
    _scale = scale; 
    [self updateUI]; 
} 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 
} 

- (void)didReceiveMemoryWarning 
{ 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

-(IBAction)changedScale:(UIStepper *)stepper { 
    self.scale = stepper.value; //this function works fine, but is not delegate/does not get called by view 
} 

-(float) scaleForGraph:(GraphView *)requestor { 
    NSLog(@"HI"); //never gets here 
} 

-(NSMutableDictionary*) valuesForGraph:(GraphView *)requestor withWidth:(float) width { 
    NSLog(@"Hello2"); //never gets here 
    } 
    return xyVals; 
} 

@end 

Answer 1

在您發佈的代碼中沒有任何地方會告訴您的GraphViewGraphingViewController是它的代表。所以，你正在發送消息給nil。

你想要做的事，如：

self.graphView.delegate = self; 

在你GraphingViewController設置代碼。

Answer 2

讓GraphView的控制器實際委託。您可以按Ctrl拖動從GraphView對象（在底部的橙色圓圈）做它在界面生成器，比選擇「委託」